Phytosterols have been found to be effective in reducing serum cholesterol in humans. Phytosterols are steroids that bear a close structural relationship to cholesterol but differ in the configuration of the side chains at the 17-position. It is well known that β-sitosterol and the fatty acid esters of β-sitosterol are effective in reducing serum cholesterol. Recent studies have found that β-sitostanol and the fatty acid esters of β-sitostanol are particularly effective in reducing serum cholesterol and LDL levels. It has been recently reported that the fatty acid esters of β-sitostanol are particularly effective cholesterol-reducing agents presumably because they are in solution. Such esters can be introduced into the body as additives in food products such as margarine. Margarines containing β-sitosterol and those containing β-sitosterol fatty acid esters as well as margarines containing β-sitostanol and β-sitostanol fatty acid esters have been shown to reduce serum cholesterol levels in humans.